Using omeprazole to link the components of the post-prandial alkaline tide in the spiny dogfish, Squalus acanthias

After a meal, dogfish exhibit a metabolic alkalosis in the bloodstream and a marked excretion of basic equivalents across the gills to the external seawater. We used the H⁺, K⁺-ATPase pump inhibitor omeprazole to determine whether these post-prandial alkaline tide events were linked to secretion of H⁺ (accompanied by Cl^–) in the stomach. Sharks were fitted with indwelling stomach tubes for pretreatment with omeprazole (five doses of 5mg omeprazole per kilogram over 48 h) or comparable volumes of vehicle (saline containing 2% DMSO) and for sampling of gastric chyme. Fish were then fed an involuntary meal by means of the stomach tube consisting of minced flatfish muscle (2% of body mass) suspended in saline (4% of body mass total volume). Omeprazole pretreatment delayed the post-prandial acidification of the gastric chyme, slowed the rise in Cl^– concentration of the chyme and altered the patterns of other ions, indicating inhibition of H⁺ and accompanying Cl^– secretion. Omeprazole also greatly attenuated the rise in arterial pH and bicarbonate concentrations and reduced the net excretion of basic equivalents to the water by 56% over 48h. Arterial blood CO₂ pressure and plasma ions were not substantially altered. These results indicate that elevated gastric H⁺ secretion (as HCl) in the digestive process is the major cause of the systemic metabolic alkalosis and the accompanying rise in base excretion across the gills that constitute the alkaline tide in the dogfish.

Stability of oxide films formed on mild steel in turbulent flow conditions of alkaline solutions at elevated temperatures

In the industries involving alkaline solutions in different process streams, the nature and stability of oxide films formed on the metallic surfaces determine the rates of erosion–corrosion of the equipment. In the present study the characteristics of the oxide films formed on AISI 1020 steel in a 2.75 M sodium hydroxide solution at temperatures up to 175°C, have been investigated by employing electrochemical techniques of cyclic voltammetry and chronoamperometry. The experiments were carried out in an autoclave system based upon a ‘rotating cylinder electrode’ geometry to determine the effects of turbulence on the stability of the films. The results suggest that little protection is afforded in the active region (at about −0.8 V_SHE). In the passive region at low potentials (−0.6 V to −0.4 V_SHE), it appears the films are compact and more stable, and therefore provide good protection. At higher potentials (>−0.4 V_SHE) in the passive region, the results suggest that film formation and dissolution occur simultaneously and the increase in temperature and turbulence causes a breakdown of the passive film resulting in a situation similar to nonprotective magnetite growth.

Novel alkaline polymer electrolytes based on tetramethyl ammonium hydroxide

In this work, novel alkaline solid polymer electrolytes (SPEs) with tetramethyl ammonium hydroxide (Me₄NOH·xH₂O) have been developed, without addition of any volatile solvent. It was found that some polymers such as poly(sodium acrylate) had good compatibility with Me₄NOH·xH₂O. The polymer-Me₄NOH·xH₂O electrolytes thus prepared in this work appeared to have improved mechanical properties as compared with the pure hydroxide and remained highly conductive in the solid state (10² S cm⁻¹ at ~40 °C). The thermal properties of the alkaline SPEs and the dependence of conductivity on composition and temperature are presented, and the relationships between properties and composition as well as conductivity mechanism for these new systems are discussed.